While genetic susceptibility and environment clearly represent realms of influence for the development of type 1 diabetes, a series of immunological abnormalities are inherent to the immune dysregulation that results in the autoimmune destruction of pancreatic (3 cells. Indeed, our previous PO1 studies of individuals with or at increased-risk for type 1 diabetes, as well as in the non-obese diabetic (NOD) mouse model of the disease, associated a series of specialized immune system cells and specific mediators with the disorder. However, issues related to the interplay between these specialized cells and the mediators that allow for abnormal immune regulation, the specificity of these immunological defects in type 1 diabetes versus other autoimmune and metabolic disorders, as well as the ontogeny of immune dysregulation in the natural history of the disease (both prior to and after onset) remain unclear. Our goal in seeking renewal of this P01 grant is to address these outstanding issues;all for the continued purpose of testing our hypothesis that antigen presenting cells (dendritic cells, macrophage/monocytes), through their interaction with components of the cellular immune system (iNKT cells, regulatory T cells), form a critical facet to the immune dysregulation which results in type 1 diabetes. This P01 renewal will examine this hypothesis through three separate but highly interactive Projects. The Projects utilize the NOD mouse model and an extremely valuable population of human subjects with or at increased-risk for type 1 diabetes, as well as healthy controls or persons with type 2 diabetes. The PO1 application is comprised of three Projects: Project 1 (S.B. Wilson, PI) - iNKT Cell Gene Expression and Effector Function in Type 1 Diabetes;Project 2 (M. Clare-Salzler, PI) - Interferons alpha/beta in Type 1 Diabetes Pathogenesis;and Project 3 (M. Atkinson, PI) - Immune Regulation and Type 1 Diabetes Pathogenesis. The projects will be supported by two well established Core facilities: A-Administration;B-Pathology &Immunology. The successful completion of these P01 studies should prove beneficial to improving our understanding of those events critical to the natural history of type 1 diabetes, identifying markers that enhance our ability to monitor cellular immune activities in the disease, uncovering the interplay between the genetics, environment and the immune response in the pathogenesis of type 1 diabetes, as well as developing immunotherapies capable of preventing or reversing the disorder. PROJECT 1: iNKT Cell Gene Expression and Effector Function in Type 1 Diabetes (PI, Wilson, S) PROJECT 1 DESCRIPTION (provided by applicant): CD1d-restricted T cells (or "iNKT cells") have been reported to regulate an extremely diverse set of immunologic responses and diseases. Dysfunction including cytokine secretion by these T cells is clearly correlated with the development of autoimmunity, and in particular autoimmune type 1 diabetes. Despite the importance of CD1d-restricted T cells in this disease, the question of how these T cells function normally and the exact nature of the disease-associated defects remains unclear. In this regard, potential regulatory functions that would be predicted to have significant impact on type 1 diabetes include recently described critical interactions of CD1d-restricted T cells with dendritic cells (DC;the focus of Project 2) and the activation-induced secretion of regulatory cytokines. Recent work has demonstrated that in normal human volunteers, the CD4+ CD1d-restricted subset preferentially secrete regulatory cytokines, whereas the CD4- (or "DM") subset were strongly biased towards the secretion of Th1-related cytokines and expressed greater levels of proteins with cytotoxic function. We have observed that individuals at risk for type 1 diabetes have a significant bias towards the DN subset. Perhaps more importantly, CD4+ iNKT cells preferentially express FOXP3 (the focus of Project 3) and secrete an as of yet to be identified factor that induces myeloid DC differentiation. Interestingly, the expression of FOXP3 is dependent on IL-2 and CD25, both of which are candidate type 1 diabetes susceptibility alleles. Thus, CD4+ CD1 d-restricted T cells might serve to prevent progression to diabetes by controlling DC maturation and effector T cells while DN CD1d-restricted T cells might promote pro-inflammatory responses. In this proposal, we plan to investigate with Projects 2 and 3, the mechanism by which CD4+ and DN iNKT cells interact and regulate T effector cells and APC. To that end, our proposal will specifically test the hypothesis that CD4+ iNKT cells are a unique class of regulatory T cells and may serve to prevent progression to autoimmune type 1 diabetes, while DN iNKT cells play a more pathogenic role. This hypothesis predicts that reduced activity of the CD4+ iNKT cell subset compared to that of the DN subset (which could result from a selective defect in CD4+ functions, or an alteration in DN vs. CD4+ proportion), could in some cases be associated with progression to type 1 diabetes. This hypothesis will be tested by performance of two specific aims involving: 1) Analyses of iNKT frequency and function, and 2) Characterization of DC differentiation factor(s) secreted by CD4+ iNKT cells. Together with Projects 2 and 3, the successful completion of these studies could lead to an improved understanding of the mechanisms underlying the autoimmune activity that that results in type 1 diabetes as well as the identification of novel factors important to immune regulation.